Method

2.2.1 Participants

Eighty-three participants from the Georgia Institute of Technology participated in this study in partial fulfillment of a course requirement. None of the participants were aware of the purpose of the study. Participants gave informed consent prior to beginning the

experiment and all participants were treated in accordance with APA guidelines.

2.2.2 Stimuli and apparatus

Stimuli presentation and RT measurements were implemented using a Dell Dimension 3000 PC with a 17” monitor. All responses were recorded to the nearest

millisecond. Manual responses were made on a Psychology Software Tools serial response box and participants viewed the visual display from a distance of approximately 60 cm.

2.2.3 SRT task

Four evenly spaced circles drawn with white lines on a black background were presented horizontally in the center of the computer monitor. The diameter of each circle subtended 3.5º of visual angle. Two circles were presented on either side of a white fixation cross; the fixation cross subtended 1.0º x 1.0º of visual angle. The two innermost circles were positioned 3.0º on either side of the fixation cross and the outermost circles were positioned 3.5º from the outer edge of the inner circles. The entire horizontal display

subtended 28º of visual angle. On each trial, one of the circles filled in (white) and this shaded circle served as the target for that trial.

Participants were randomly assigned to the NoSwitch, Perceptual and Response groups. All participants performed 12 blocks of 96 trials each. Blocks 1-8 constituted the training phase and Blocks 9-12 constituted the testing phase (Table 1). Sequence learning in the training phase was measured behaviorally by comparing RTs from Block 7 to RTs from Block 8; during the testing phase, sequence learning was measured by comparing RTs from Block 11 to the average RT from Blocks 10 and 12. This was the transfer effect (Table 1).

Table 1. Block Design for Experiment 1

2.2.4 The sequence

Six sequences were used in the SRT task. The sequences followed the statistical rules defined by Reed and Johnson (1994). The same sequence was used in the sequenced blocks (Blocks 2-7 and Block 11) and a different sequence matched for simple frequency

information was used in each of the random blocks (Block 1, 8-10 and 12). Sequences were counterbalanced across participants.

2.2.5 Procedure

For all groups, the four circles and the fixation cross were presented on the screen at the start of each trial. This display remained on the screen for 2000ms before the start of the first trial. When a trial began, a target appeared in one of the four locations and remained on the screen for 100ms. Participants were instructed to respond to the targets as quickly and accurately as possible using their middle and index fingers of each hand. The circles and the fixation cross remained on the screen for the duration of the trial. The next trial began 250ms after a response had been made.

For all groups, Block 1 was an unsequenced1 block, Blocks 2-7 were sequenced blocks, Blocks 8-10 were unsequenced blocks, Block 11 was a sequenced block and Block 12 was an unsequenced block (Table 1). As shown in Figure 2, when using the direct S-R mapping (Perceptual and Response groups; testing phase), participants respond to the circles from left to right with their left middle, left index, right index and right middle fingers respectively and when using the indirect S-R mapping (all groups; training phase. NoSwitch group; testing phase), participants respond to the circles from left to right with their right index, left middle, right middle and left index fingers respectively.

At the end of each block a screen was displayed informing participants of their accuracy as well as their mean RT for that block. At that time participants were also encouraged to respond as quickly and accurately as possible in the upcoming block.

Before the start of the experiment, participants completed four (NoSwitch group) or five (Perceptual and Response groups) practice blocks. These practice blocks were designed to familiarize participants with each mapping so that they would perform accurately during

the experiment. These practice blocks were methodologically identical to the actual experimental blocks except that the target positions were always random and the blocks consisted of 40 trials each. Also, RT and accuracy feedback was given following each trial and at the end of each block. The NoSwitch group completed four blocks of trials using the indirect S-R mapping. The Perceptual and NoSwitch groups each completed one block of trials using the direct S-R mapping and four blocks of trials using the indirect S-R mapping.

After the experiment ended, all participants completed two direct tests of sequence learning. The first asked the following three questions (Frensch, Wenke, & Runger, 1999): What do you believe is the goal of this experiment? Did you notice that the shaded circles were presented in a certain sequence? Please describe whatever you noticed about the sequence. Regardless of their answers to the first set of questions, participants were asked complete a free-generation task. Before the free-generation task, participants were informed that the targets actually followed a repeating sequence and they were then asked to reproduce the sequence using up to 30 button-pushes. Their responses were echoed on the screen. They were then debriefed and issued credit.

2.3 Results and Discussion